Re: [PATCH 1/7] block/nbd: avoid touching freed connect_thread

[Roman Kagan]

On Mon, Mar 15, 2021 at 06:40:12PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> 15.03.2021 09:06, Roman Kagan wrote:
> > When the NBD connection is being torn down, the connection thread gets
> > canceled and "detached", meaning it is about to get freed.
> > 
> > If this happens while the connection coroutine yielded waiting for the
> > connection thread to complete, when it resumes it may access the
> > invalidated connection thread data.
> > 
> > To prevent this, revalidate the ->connect_thread pointer in
> > nbd_co_establish_connection_cancel before using after the the yield.
> > 
> > Signed-off-by: Roman Kagan <rvkagan@yandex-team.ru>
> 
> Seems possible. Do you have a reproducer? Would be great to make an iotest.

It triggered on me in iotest 277, but seems to be timing-dependent.
I'll see if I can do it reliable.

Thanks,
Roman.